The role of dysprosium ions as a dopant on linear and nonlinear optical dispersion parameters in a-Se thin film

Thin films of un-doped and doped a-Se with Dysprosium rare-earth ions have been prepared by the thermal evaporation technique. The optical transmission spectra of the investigated films have been measured in a wide spectral range and used to calculate the linear optical constants together with the optical energy gap of studied films. The observed decrease in the values of the energy gap against the increase of the Dysprosium (Dy) content in a-Se films has been explained using Mott and Davis Model and in terms of electronegativity difference of the constituent atoms. Furthermore, the dispersion of nonlinear parameters such as second-order refractive index and nonlinear absorption coefficient (two-photon absorption coefficient) of investigated films are presented and discussed.

Linear and Nonlinear Absorption of Titanium Dioxide Films Produced by Plasma Ion-Assisted Electron Beam Evaporation: Modeling and Experiments

Titanium dioxide films were prepared by plasma ion-assisted electron beam evaporation. Linear optical properties were investigated in terms of spectrophotometry using the beta-distributed oscillator (ß_do) model as a parametrized dispersion law. The nonlinear two-photon absorption coefficient of titanium dioxide was determined by means of the laser-induced deflection technique at a wavelength of 800 nm. The obtained values of (2–5) × 10−11 cm/W were consistent with published experimental values for rutile as well as for simulations performed in the frames of the ß_do and Sheik–Bahae models.

ANGULAR DEPENDENCE OF TWO-PHOTON ABSORPTION IN CdP2

In CdP2 linearly circular dichroism and frequency dependence of the two-photon absorption coefficient р have been studied in detail, however, we do not know the value of the absolute value of в and its dependence on polarization azimuth. Purpose of research: testing of possibilities of direct method of measuring the coefficient of two- photon absorption in solids. Object of research - monorcycles CdP2. The research method is experimental. The angular dependence of the two-photon absorption coefficient CdP2 and the intensity of light at the sample output is established. When designing and manufacturing elements of power optics and correlators from univalent crystals, one must take into account the following dependencies. KEYWORDS: POLARIZATION, TWO-PHOTON ABSORPTION, CdP2, POLARIZATION AZIMUTH

Third-Order Nonlinear Spectrum of GaN under Femtosecond-Pulse Excitation from the Visible to the Near Infrared

Gallium nitride (GaN) has been established as a promising candidate for integrated electro-optic and photonic devices, aiming at applications from optical switching to signal processing. Studies of its optical nonlinearities, however, lack spectral coverage, especially in the telecommunications range. In this study, we measured the two-photon absorption coefficient (β) and the nonlinear index of refraction (n2) of GaN from the visible to the near-infrared by using femtosecond laser pulses. We observed an increase of β from (1.0 ± 0.2) to (2.9 ± 0.6) ×10−11 m/W as the photon energy approached the band gap from 1.77 up to 2.25 eV (700–550 nm), while n2 varied from (90 ± 30) ×10−20 up to (265 ± 80) ×10−20 m2/W within a broad spectral range, from 0.80 up to 2.25 eV (1550–550 nm). The results were modeled by applying a theory based on the second-order perturbation theory and the Kramers-Kronig relationship for direct-gap semiconductors, which are important for the development of GaN-based nonlinear photonic devices.

Nonlinear Metasurface for Structured Light with Tunable Orbital Angular Momentum

Orbital angular momentum (OAM) beams may create a new paradigm for the future classical and quantum communication systems. A majority of existing OAM beam converters are bulky, slow, and cannot withstand high powers. Here, we design and experimentally demonstrate an ultra-fast, compact chalcogenide-based all-dielectric metasurface beam converter which has the ability to transform a Hermite–Gaussian (HG) beam into a beam carrying an OAM at near infrared wavelength. Depending on the input beam intensity, the topological charge carried by the output OAM beam can be switched between positive and negative. The device provides high transmission efficiency and is fabricated by a standard electron beam lithography. Arsenic trisulfide (As 2 S 3 ) chalcogenide glass (ChG) offers ultra-fast and large third-order nonlinearity as well as a low two-photon absorption coefficient in the near infrared spectral range.